Different Title Tags To GoogleBot & GoogleBot Mobile

What if you serve GoogleBot one title tag and GoogleBot Mobile a different title tags/attributes? Google's John Mueller said that Google would likely just ignore it, or maybe just pick one? Here are the tweets:

GoogleBot for mobile and desktop are very similar these days and when Google goes full-on with the mobile first index then things will flip. So make sure not to try to play games with Google here, especially now.